1. Technical Field of the Invention
The present invention relates generally to an improvement on a gas sensor which may be employed in an oxygen measuring device of an air-fuel ratio control system measuring an oxygen content in exhaust gasses of an internal combustion engine of automotive vehicles.
2. Background of Related Art
For burning control of fuel in internal combustion engines of automotive vehicles, an air-fuel ratio sensor is installed in an exhaust system to measure an air-fuel ratio. Such an air-fuel ratio sensor is usually implemented with an oxygen sensor which has a pair of electrodes one of which is exposed to a gas to be measured and the other is exposed to a reference gas introduced into a reference gas chamber from the outside of the oxygen sensor.
In recent years, in order to improve installation of the oxygen sensor in the vehicle and decrease manufacturing costs thereof, the size of the oxygen sensor is required to be decreased. To this end, there has been proposed an improved structure in which the length of the oxygen sensor is shortened, and an outer cover or other parts are joined by crimping. The crimping, however, leads to a problem of reducing an area of a gas passage introducing the reference gas into the reference gas chamber, which will cause the flow of the reference gas to be lowered, resulting in a decrease in measuring accuracy.